The present invention relates to a process for the preparation of phenyl carbonates or polycarbonates. More particularly, the present invention allows for the preparation of phenyl carbonates or polycarbonates utilizing as reactants a corresponding phenol or bisphenol; methanol; carbon monoxide; and oxygen.
In U.S. Pat. No. 4,182,726 a process for preparing aromatic carbonates utilizing Lewis acids to catalyze the transesterification of phenols or acyl esters thereof with an alkyl carbonate or an aryl alkyl carbonate was disclosed.
In U.S. Pat. No. 4,533,504 an integrated process for the preparation of aromatic carbonates was disclosed wherein the methyl acetate by-product formed in the transesterification of a phenyl ester with a dialkyl carbonate was recycled by heating the alkyl ester to form a ketene and subsequently such ketene was reconverted by reaction with a phenol to form additional quantities of the phenyl ester.
Preparation of a ketene intermediate has proven costly and inefficient due to the high temperatures involved. Recoveries on the order of only about 80% of theoretical or less are typical leading to the need to develop a more efficient means of generating phenyl carbonate precursors and disposing of alkyl ester by-products.
In U.S. Pat. No. 4,452,968 an integrated process for the preparation of aromatic polycarbonates was disclosed wherein the methyl acetate by-product formed in the transesterification of a bisphenol diacetate with a dialkyl carbonate was recycled by heating the alkyl ester to form a ketene and subsequently such ketene was reconverted by reaction with a bisphenol to form additional quantities of the bisphenol diacetate. For the teachings contained therein the above identified patent is incorporated herein by reference thereto. As mentioned above, preparation of a ketene intermediate has proven costly and inefficient due to the high temperatures involved, leading to the need to develop a more efficient means of generating polycarbonate resins and recycling of alkyl ester by-products.